There are innumerable environments having need for covering both hot and cold ducts with heat insulating material in a low cost expeditious manner and the exterior of which is free of depressions, crevices and the like in which foreign matter can collect and present difficult removal problems. Examples include food and drug processing establishments, hospitals, clean rooms for the manufacture of high precision products, etc.
Many proposals to meet these needs embody laminated heat insulating jackets provided with separable interlockable seams. Illustrative United States patents disclosing such jackets include Plummer No. 3,092,530; Eichberg No. 3,638,286; Plummer No. 3,682,163; Plummer No. 3,858,282 and Plummer No. 3,925,856. In all except the first mentioned one of these patents the interlocking seam members exhibit outwardly exposed crevices, pockets and the like extending lengthwise of the seam in which food stuff and foreign matter generally can become deposited, rendering the jacket unsanitary and difficult if not impossible to cleanse. It has been common practice particularly in jackets made to embrace conductors and cabling to provide a seamed jacket with a guard flap bridging the interior side of the seam members and effective to provide an electrical shielding layer embracing the cabling as well as a guard preventing the jacket contents to interfere with closure of the seam. The first mentioned one of the Plummer patents also shows a jacket with a guard flap bridging the exterior of the plastic seam members and coated with heat reflecting material to protect the plastic seam from momentary high temperatures occasioned by the launching of rockets and the like. The objective served is the prevention of damage to the plastic seam by the temporary high temperatures.
Prior to this invention applicant's assignee and his competitors have been utilizing heat insulating jackets having an external guard flap bridging the seam members but each of these involves laborious and time consuming operations to hold the guard flap pressed against the exterior of the jacket body. For example, prior to this invention, my assignee relied upon elongated rigid members held pressed against the flap by a multiplicity of temporary tie bands. While the guard flap is so held caulking compound was applied along the edge of the guard flap and allowed to take a set before removing the restraining bands and the rigid members. This technique requiring the joint efforts of two or more workmen requires an excessive amount of assembly and disassembly time by costly labor as well as a waiting period for the caulking to take a set with the possibility that portions will exhibit an unsealed gap and recesses for the collection of foreign material. Longitudinally slit heat insulating jackets have also been proposed which rely upon pressure sensitive adhesive applied to the lateral extension of one edge of the outer jacket layer to hold the jacket assembled about tubing. Such jackets present assembly problems owing to the skill required in holding the adhesive free of contact with the jacket while at the same time holding the jacket as a whole snugly contracted and closed about the tubing. Furthermore, upon release of the contracting forces, the adhesive is placed under shear stresses and may fail prematurely thereby allowing partial if not complete disassembly of the jacket.